Half height magnetooptical-disk recording and/or reproducing apparatus for a 5.25 inch large capacity magnetooptical-disk

ABSTRACT

An optical disk recording and/or reproducing apparatus is provided which is capable of storing a large amount of information, transferring data at a high speed, supporting SCSI-1 and SCSI-2, and the reducing the size of the apparatus, particularly the height (to the so-called half height), The magnetooptical-disk recording and/or reproducing apparatus of the invention is of the same size as that of the 5.25-inch magnetic disk recording and/or reproducing apparatus of half height, or it is 146 mm wide, 203 mm deep, and 41.3 mm high. The front panel 1 has the cartridge slot 2 and cartridge ejection button 3 provided thereon so that a cartridge including a disk for recording and reproducing information is inserted in or ejected from the apparatus. The cartridge insertion slot 2 has a double flap provided so that at least one part of the double flap closes the slot, preventing dust from entering through the cartridge slot 2 except when the cartridge is inserted in or ejected from the apparatus, According to this invention, the magnetooptical-disk recording and/or reproducing apparatus can record information of 1 GB/side or above on the disk and has the size of half height.

BACKGROUND OF THE INVENTION

This invention relates to a recording and/or reproducing apparatus for a5.25-inch large-capacity magnetooptical-disk.

The conventional 5.25-inch magnetooptical-disk recording and/orreproducing apparatus drives a magnetooptical-disk of 325 MB/side, whichis standardized by ISO/IEC 10089, to rotate it at 2400 rpm, and recordsor reproduces information on or from each side of the disk. In thiscase, the data transfer rate is 920 KB/s. In addition, the interface tothe host interface is SCSI-1, and the apparatus size is the same as the5.25-inch magnetic disk recording and/or reproducing apparatus of fullheight (140 mm×208 mm×82.6 mm).

The bias magnetic field generator of the magnetooptical-disk recordingand/or reproducing apparatus, upon recording, applies a verticalmagnetic field to the recording medium in one direction, and uponerasing, applies the field to it in the other direction, or oppositedirection. This magnetic field, in cooperation with the action of thevery small light spot formed on the recording medium through an objectlens, acts to erase data from or record data on the recording medium.The bias magnetic field generator is of the electromagnet coil type orof the permanent magnet type.

The conventional bias magnetic field generator of the electromagnet coilor permanent magnet type is so provided that the light spot can beformed along the center line of the bias magnetic field generator on therecording medium. An example of the provision of an electromagnet coilon the opposite side of the recording medium to the object lens isdescribed in JP-A-59-203258. An example of the provision of anelectromagnet on the object-lens side of the recording medium isdescribed in JP-A-57-27449. On the other hand, an example of theprovision of a permanent magnet on the opposite side of the recordingmedium to the object lens is described in JP-A-57-24047. However, thereis no idea that the permanent magnet is disposed on the object-lens sideof the recording medium.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a novelmagnetooptical-disk recording and/or reproducing apparatus which canmeet the user's various demands.

The user ardently demands a new-type apparatus of a large capacity, highdata transfer rate, SCSI-1 and 2 support, and small size, particularlylow height (, or the so-called half height) over the conventional5.25-inch magnetooptical-disk recording/reproducing apparatus. Inaddition, the problem of dust collecting in the conventional opticaldisk apparatus must be solved. The standard disk of 325 MB/side whichmeets the specification ISO/IEC 10089 is also demanded to have therecording and/or reproducing function (the so-called backwardcompatibility).

Moreover, the apparatus must be able to be placed with its side down aswell as with its top up. The housing designed for the conventionalmagnetic disk apparatus must also be able to be simply used in themagnetooptical-disk apparatus. Of course, it must also be able to usevarious disks of many makers such as the second vendors or thirdvendors.

The increase of the storage capacity can be achieved by use of the marklength recording system, ZCAV (Zoned Constant Angular Velocity)recording system and the combination of a 780-nm or 670-nm semiconductorlaser and a large NA (Numerical Aperture) (for example, 0.55 or above)object lens.

In the CAV recording system the recording density decreases inproportion to the radius of the disk, while in the ZCAV recording systemthe recording region of the disk is divided into a large number of zonesin the radius direction so that the recording density is keptsubstantially constant in the radius direction of the disk. Therefore,in the ZCAV recording system the storage capacity can be increased toabout 1.5 times as large as that in the conventional CAV recordingsystem.

The mark length recording was difficult for the magnetooptical-diskbecause the optimum recording power greatly depends on the environmentaltemperature and because the thermal diffusion of the recording film islarge. However, it can be achieved by use of the double PLL (PhaseLocked Loop) system, trial writing control system, 1-7 modulation systemand direct edge detection system.

The mark length recording system is able to increase the storagecapacity theoretically twice as large as the mark position recordingsystem (in which a piece of information is recorded by a singlerecording mark) because two pieces of information can be recorded by asingle recording mark. In practice, the mark length recording system hasa difficulty of its own, and thus it is possible to achieve about1.7-times increase of storage capacity. Particularly, since themagnetooptical-disk recording is substantially thermomagnetic, the marklength to be recorded greatly depends on the temperature and recordingsensitivity of the disk, and thus it is difficult to record each marklength which has information on its edge. However, since the disktemperature and the recording power are not suddenly changed, the marklength expansion or compression is substantially constant within onesector as a unit for recording.

Therefore, since a desired distance can be obtained between the frontedges or rear edges, correct data can be discriminated from thereproduced signal even under slight expansion or compression of marklength by the action of data discrimination PLL separately to each ofthe front edge and the rear edge (double PLL). Use of the double PLLsystem makes it possible to allow for slight expansion or compression ofmark length, but the high-density recording, or large increase ofstorage capacity is substantially difficult to realize by only thedouble PLL. Since the magnetooptical-disk medium has a very largethermal diffusion constant, the increase of the recording density willaffect the resolution of the reproduced signal.

The trial writing control is the new technique for obviating thisdifficulty to achieve great increase of storage capacity. In otherwords, a proper time after the disk is loaded into the apparatus, trialwriting is made on one or more particular regions of the disk in orderto search for optimum recording power and thereby to remove the effectof the temperature and sensitivity of the disk and make correct marklength recording. The trial writing control is also used for therecovery of recording error. When a certain kind of recording erroroccurs (for example, when the number of error bytes within one sectorexceeds 30 bytes), trial writing is made to reset the optimum recordingpower, and recording is again performed.

Since the 1-7 modulation system has a wider window width for datadiscrimination than the 2-7 modulation system, an allowable edgeposition variation in mark length recording is large. Also, since the1-7 modulation system employs a narrow frequency band, it has a high S/Nratio and is suited to increase the recording density.

In the direct edge detection system, since noise in the high-frequencyregion is not amplified, the S/N ratio can be improved and thusrecording density can be increased as compared with the differentialdetection system.

In the ZCAV recording system, since the data transfer rate changes ineach zone, clocks of different oscillation frequencies are necessary tocontrol the data transfer rate, thus making the circuit systemcomplicated. Therefore, this ZCAV recording system was thought not to besuited for a small size apparatus. However, use of alarge-scale-integrated synthesizer will solve this problem withoutmaking the circuit system complicated.

A 780-nm or 680-nm semiconductor laser and a large-NA (0.55 or above)object lens are used to reduce the size of the light spot. In general,when the light spot size is reduced, the distortion of the reproducedsignal is increased with the aberration and defocus of the optical spot,thus reducing the reliability of data. This problem can be solved byadding an equalizing circuit to the reproducing circuit system.

In addition, a 780-nm or 670-nm semiconductor laser and a large-NA (forexample, 0.55) focus lens are used to reduce the light spot size asabout 1/1.1 or 1/1.3 compare with the combination of a 830-nmsemiconductor laser and 0.53-NA focus lens and hence the recordingdensity can be increased about 1.2 times or 1.6 times.

Since the equalizing circuit added to the reproducing system cancompensate for the reduction of the resolution due to the aberration anddefocus of the light spot, the reproduced signal can be stably obtainedand correct data can be reproduced from the high-density recorded disk.

The data transfer rate can be increased together with the increase ofstorage capacity by rotating the disk at 2400 rpm or above as in theprior art since the large storage capacity results in increase of bitdensity.

A microprogram for controlling the SCSI controller is contrived in orderto support both host interface SCSI-1 and SCSI-2, and thereby themicroprogram is not greatly increased.

The half height of the apparatus size can be achieved by using a singlemain circuit board and thin mechanical system. The realization of asingle main circuit board can be promoted by the large-scale integrationof the circuit system. The difficulty in realizing a thin mechanicalsystem occurs in the recording/erasing magnetic field generationmechanism. In general, the recording/erasing magnetic field generationmechanism is a rotating magnet or electromagnetic coil. In theconventional apparatus, either one of the magnet and electromagneticcoil is disposed on the opposite side of the disk to the optical head,thus remarkably preventing the half height design. For the half heightdesign of the apparatus, it is effective to reduce the size of therecording/reproducing magnetic field generation mechanism and to placeit on the same side as the optical head.

The now practically used magnetooptical-disk medium of, for example, 130mm in diameter, needs to be applied with a bias magnetic field of 18000A/m to 48000 A/m vertically up or down, and with the laser spot. Thebias magnetic field generator is required to apply a magnetic field ofthe above intensity on the surface of the recording medium on which thebeam spot is formed. In this case, the magnetic field must be applied onthe recording film through a disk substrate of 1.2 mm thick of which thesurface is vibrating at an amplitude of about 0.4 mm. Therefore, in theelectromagnet coil system, although erasing and recording operations canbe switched by only changing the direction of the current which iscaused to flow in the electromagnet coil, the electromagnet coil becomeslarge since it has a necessary product of the number of turns of theelectromagnet coil and the current flowing in the coil, or a necessaryampereturn. Thus, it is very difficult to mount this coil on the objectlens. Although the electromagnet coil can be provided adjacent to theobject lens, the distance between the focused beam spot and theelectromagnet coil is great, and thus the necessary ampereturn isfurther increased. For example, the electromagnet coil is required tohave a thickness, or height of about 10 mm, and thus it is difficult toprovide the electromagnet coil of a practical size on the object lensside. Thus, because of the above aspects, the electromagnet coil isgenerally provided on the opposite side of the recording medium to theobject lens.

On the other hand, in the permanent magnet system, the magnet itself canbe produced to be smaller than the electromagnet. There is an example ofthe bias magnetic field generator for rotating the permanent magnet ofwhich the diameter is in a range from 3 to 4 mm. In this case, since itis necessary to rotate the permanent magnet in order to switch theerasing and recording operations, the magnet system still requires aspace of which the height is about 10 mm including the height of therotation support mechanism of the permanent magnet and the height of theattached mechanical portion of the drive coil and so on. Therefore, itis difficult to mount the permanent magnet on the object lens drive, andthus in the prior art the permanent magnet is not provided on the objectlens side.

Since the bias magnetic field generator is provided on the opposite sideof the recording medium to the object lens as described above, theoptical disk recording/reproducing apparatus must have a total height ofthe object lens drive actuator height, optical disk cartridge height andbias magnetic field generator height, and thus there is a difficulty inreducing the height.

According to this invention, the permanent magnet type bias magneticfield generator can be provided on the object lens side of the opticaldisk, or recording medium so that the apparatus can be small-sized andreduced in its height.

As to the dust prevention means, a cartridge including a disk is loadedinto the apparatus, and the optical head and the disk can be shut outfrom the outside and tightly closed. Thus, the dust provision of thismagnetooptical-disk apparatus can be greatly improved over that of theconventional optical disk apparatus. When the apparatus is tightlyclosed, the temperature within the apparatus will greatly increase, butit can be solved by placing the single circuit board out of the closedspace.

As to the so-called backward compatibility function, two functions areincorporated in one apparatus, and thus generally make the apparatuscomplicated, and therefore it is said that the half height of apparatusis difficult. However, if the physical shapes of the disk of 1 GB/sideor above and the cartridge are made coincident with those of thecartridge and disk which are standardized under the specificationISO/IEC 10089, the mechanical system can be shared. Since the opticalhead is improved to have a smaller beam spot than in the conventionalrecording and/or reproducing apparatus and thus is able to obtain dataat a high resolution, there is no problem even in sharing the mechanicalsystem. Therefore, a problem will occur with the circuit system.However, since the servo/access system can be used by changing the gainof the servo system and by slight change of the logic, the number ofelements of the circuit system is almost not increased. The recordingand reproducing systems are different in the recording method (pitposition recording and mark length recording) and modulation code (2-7modulation and 1-7 modulation), and thus two different systems arefundamentally necessary for recording and reproduction. Therefore, foruse of a single circuit board including all the circuits, it isnaturally necessary to increase the rate of the large-scale integration,and further it is necessary to make sharing as much as possible and tothereby decrease the number of circuits. To this end, if a recordingformat is contrived for 1 GB/side or above, the clock for recording andreproduction can be produced as one of the outputs from theabove-mentioned synthesizer. In other words, one crystal oscillator canbe saved which is normally used to produce a new recording andreproducing clock in order to make the backward compatibility function.In addition, one part of the above-mentioned double PLL for mark lengthrecording may be used for the PLL for data discrimination.

When the apparatus is designed to be capable of being set up normally,or with its top up and set with its side down, a problem is caused withthe two-dimensional actuator. The two-dimensional actuator is desired tobe of the pin support type when considering the high-speed accessperformance. However, when the apparatus is placed with its top or withits side down, the life of the pins may be shortened. If a gravitycompensation mechanism is added, the life can be prevented from beingshortened, and thus the apparatus can be placed in both top-up positionand side-down position.

In order that the housing for the magnetic disk can be directly used forthe magnetooptical-disk without change, it is necessary to make the sizeof the magnetooptical-disk apparatus coincident with that of themagnetic disk apparatus (, or make the half height), make the tappedholes for fixing to the housing at the same positions as in the magneticdisk apparatus, and provide the connector for the interface SCSI to thehost apparatus at the back of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exterior view of one embodiment of a magnetooptical-diskrecording and/or reproducing apparatus of the invention.

FIGS. 2A and 2B are views of the mechanism of the magnetooptical-diskrecording and/or reproducing apparatus shown in FIG. 1.

FIG. 3 is a cross-sectional view of a main part of an example of themovable head which is used in the magnetooptical-disk recording and/orreproducing apparatus of the invention.

FIG. 4 is a plan view of the main part of the example of the movablehead shown in FIG. 3.

FIGS. 5A and 5B are respectively perspective and front views of themovable head of the magnetooptical-disk recording and/or reproducingapparatus.

FIG. 6 is a perspective view of a saddle-shaped coil for the bias magnetdrive.

FIG. 7 is a cross-sectional view of the bias magnetic field generator.

FIG. 8 is a circuit block diagram of the control system for the biasmagnetic field generator.

FIG. 9 is a graph showing the relation between each signal and themagnetic field when the bias magnet is turned once.

FIG. 10 is a graph showing the relation between the drive current andthe rotation of the magnet when the bias magnetic field is reversed.

FIGS. 11A and 11B show examples of the use of the magnetooptical-diskrecording and/or reproducing apparatus of the invention in aninformation processing system.

FIG. 12 is a perspective view of one embodiment of themagnetooptical-disk recording and/or reproducing apparatus of theinvention.

FIG. 13 is a circuit block diagram useful for explaining the recordingand reproducing operations.

FIG. 14 is a circuit block diagram of one example of the photoelectricconverter of the optical head.

FIG. 15 is a table showing one example of the zone division in theuser's region of the disk.

FIG. 16 is a table showing another example of the zone division in theuser's region of the disk.

FIG. 17 is a circuit block diagram of one example of the synthesizer.

FIG. 18 is a circuit block diagram of one example of the reproducedsignal processing circuit.

FIG. 19 is a circuit block diagram of one example of the equalizingcircuit.

FIG. 20 is a graph for explaining the effect of the equalizing circuit.

FIG. 21 is a table showing the modulation rule of the 1-7 modulationsystem.

FIG. 22 is a table showing the comparison between the characteristics ofthe 1-7 modulation system and 2-7 modulation system.

FIGS. 23A, 23B and 23C are diagrams useful for explaining the trialwriting control system, and respectively show the reproduced signal, thesampling pulses and the recording power conditions.

FIG. 24 shows one example of the table of the support command.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will be described with reference to theaccompanying drawings.

FIG. 1 is an exterior view of one embodiment of the magnetooptical-diskrecording and/or reproducing apparatus of the invention. Thismagnetooptical-disk recording and/or reproducing apparatus has the samesize as the 5.25-inch half-height magnetic disk recording and/orreproducing apparatus. The external size is 146 mm wide, 203 mm deep,and 41.3 mm high. The front panel, 101, of the apparatus has a slot 102for the cartridge and an ejection button 103 for the cartridge. Thus,the cartridge having housed therein a disk for recording and/orreproducing information can be manually inserted into or ejected fromthe apparatus. The slot 102 for the cartridge has two flaps provided sothat at least one of the flaps closes the slot except when the cartridgeis inserted or ejected, thereby minimizing the dust which will enterinto the slot 102.

FIGS. 2A and 2B show the construction of a main part of themagnetooptical-disk recording and/or reproducing apparatus illustratedin FIG. 1. FIG. 2A is a front view of the apparatus, and FIG. 2B is aside view of the apparatus.

A circuit board 104 having main circuit components connected is mountedin the apparatus with its component side facing the bottom of theapparatus so that the components can be easily cooled. A connector 105for the SCSI interface is provided at the back end of this circuit board104 so that the interface cable can be connected to or disconnected fromthe back of the apparatus. When this apparatus is placed in a separatehousing and used, this apparatus is fixed to the housing at tapped holes120 which are provided at the same positions as those in the 5.25-inchlike-size (half height) magnetic disk recording and/or reproducingapparatus.

The optical head for recording and/or reproducing a signal has twoportions, or a fixed portion 106 and a movable portion 107. The movableportion 107 includes one carriage case 25, and has the pin supportpotation type two-dimensional actuator and the rotatable magnet mountedon this carriage case 25 as shown in FIGS. 3 and 4. The movable portion107 including the carriage case 25 is 13.5 mm high and is much thinnerthan that of the conventional optical head. In addition, since themagnet for recording and erasing which is provided on the opposite sideof the disk to the optical head in the prior art is provided on theoptical-head side, no space is necessary in which the magnet orelectromagnetic coil is provided on the cartridge holder, 108, thusgreatly contributing to the reduction of the height of this apparatus.

The bias magnetic field generator is provided along the surface of themagnetooptical-disk recording medium and on the opposite side of theobject lens to the object lens drive and support means.

The permanent magnet of the bias magnetic field generator and therotating means for this permanent magnet can be housed in a tightlyclosed container. In this case, the drive coil for driving the permanentmagnet is integrally formed to be buried in this tightly closedcontainer as a part of the container.

The permanent magnet itself of the bias magnetic field generator isconstructed to rotate as a rotor. It can be driven to rotate by themagnetic field from the permanent magnet and the drive current flowingin the drive coil of the permanent magnet. In this case, the permanentmagnet is magnetized in the direction of the rotation diameter, and thedrive coil of the permanent magnet can be constructed to have a portionwhich faces both the N-pole and S-pole of the permanent magnet and whichis parallel to the rotation axis of the permanent magnet.

Also, in this case, the permanent magnet can be disposed on the oppositeside of the object lens to the object lens drive and support means insuch a manner that the rotation axis of the permanent magnet is parallelto the surface of the magnetooptical-disk and in the radius direction ofthe disk.

As described above, when an electromagnet coil is used for the biasmagnetic field generator, the electromagnet coil size becomes largebecause of a necessary ampereturn, and thus it is difficult to mount theelectromagnet coil on or close to the object lens.

On the other hand, the permanent magnet is difficult to be incorporatedon the object lens drive because it requires a rotation mechanism asdescribed above. However, since a strong permanent magnet is alreadydeveloped, this strong permanent magnet of several mm in diameter can beused to apply a magnetic field of the above-given value, 18000 A/m orabove to the focused beam spot when it is provided on the object lensside of the recording medium and close to the object lens drive.

FIGS. 3 and 4 show a main portion of the optical movable head in oneembodiment of the invention. This head is of the separation opticalsystem type in which only the portion around the object lens is moved inthe radius direction of the recording medium and most part of theoptical system is housed in the fixed portion. FIG. 4 is a plan view ofthe main portion of the optical movable head, and FIG. 3 is across-sectional view taken along a line III--III in FIG. 4.

The carriage case 25 shown in FIGS. 3 and 4 has course coils (drivecoils) 23 mounted at the opposite ends as shown in FIGS. 5A and 5B. Themovable portion 107 can be moved at a high speed in the radius directionof the disk by the drive coils and magnetic circuits 24. The carriagecase 25 is guided by ball bearings 22 along guide shafts 21. Themagnetic circuit 24 has a magnet 210 and a yoke 220 provided in parallelto the surface of the inserted disk. Thus, the height of the magneticcircuit 24 can be considerably reduced to as low as 9.5 mm.

The fixed portion 106, though not shown in detail, has a semiconductorlaser mounted as a light source. The laser beam emitted from thesemiconductor laser is converted into a parallel beam by a collimatorlens, and further converted into a substantially-circular parallel beamby a beam shaping prism. This beam is then conducted into the movableportion 107. The laser beam from the movable portion 107 is separatedinto a desired luminous flux by a beam splitter which is provided withinthe fixed portion 106. This luminous flux is received by an opticaldetector which has a photosensitive portion of a desired shape. Thisoptical detector is used to reproduce a preformat signal which is formedat the very small pits on the disk surface, detect the control signalsfor focus servo and tracking servo, and reproduce a magnetoopticalsignal.

The carriage case 25 having the two-dimensional actuator and biasmagnetic field generator mounted is disposed to face themagnetooptical-disk which has the substrate 2 and the recording film 1formed on the base. The carriage case 25, as shown in FIGS. 5A and 5B,is guided by the ball bearings 22 along the guide shafts 21 which arefixed to a base not shown, and can be moved in the radius direction(perpendicular to the drawing sheet of FIGS. 3, 5A and 5B) of themagnetooptical-disk. The drive coils 23 are mounted on the opposite endsof the carriage case 25 and interact with the magnetic circuits 24 so asto produce an electromagnetic force, by which the carriage case 25 ismoved in the radius direction of the magnetooptical-disk.

The carriage case 25 includes, as shown in FIGS. 3 and 4, thetwo-dimensional actuator for moving the object lens 3 both in thedirection perpendicular to the magnetooptical-disk surface(perpendicular to the drawing sheet of FIG. 4), or in the AF (automaticfocusing) direction, and in the radius direction of themagnetooptical-disk (parallel to the drawing sheet of FIG. 4), or in theTR (tracking) direction. The carriage case 25 also includes a beamraising mirror 26 which is disposed at an angle of 45 degrees in orderto reflect at right angles the parallel beam which enters into thecarriage case 25 from the fixed optical system. In addition, thecarriage case 25 includes the bias magnetic field generator whichapplies a vertical bias magnetic field to the recording film 1. Thetwo-dimensional actuator has a movable portion on which the object lens3 is mounted, a support shaft 5 for slidably supporting the movableportion, and a magnetic circuit. The movable portion is formed of a lenssupport member 4 which has the object lens 3 mounted at its tip, AF(automatic focus) coils 6a, 6b which are fixed on both sides of thecentral portion of the lens support member 4, and TR (tracking) coils7a, 7b which are fixed to both sides of the rear portion of the lenssupport member 4. The lens support member 4 has a guide aperture boredat the center of the gravity of the movable portion. The support shaft 5is engaged in the guide aperture so as to guide the movable portion tomove straight in the AF direction and to rotate around the support shaft5. The magnetic circuit has a back yoke 10a, 10b, magnets 8a and 9a, 8band 9b of opposite polarities fixed to the yoke (if the front side andback side of the magnet 8a are the polarity N and S, respectively, thefront side and back side of the magnet 9a are the polarity S and N,respectively). The back yoke 10a, 10b has a center yoke 11a, 11bconnected on the bottom of the carriage case 25 as shown in FIG. 4. Themain portion of this center yoke 11a, 11b is upright within the AF coil6a, 6b. A part of the AF coil 6a, 6b is inserted between the magnet 8a,8b and the center yoke 11a, 11b. The object-lens side of the TR coil 7a,7b is inserted between the magnet 8a, 8b and the center yoke 11a, 11b,and the opposite side thereof faces the magnet 9a, 9b. The extensions ofthe back yoke 10a, 10b and the lens support member 4 are connected bysupport springs 12a through 12d so that the object lens 3 can be alignedwith reference positions in the direction perpendicular to themagnetooptical-disk surface and in the radius direction of themagnetooptical-disk.

As illustrated in FIG. 4, the magnetic flux passing between the frontside of the magnet 8a, 8b and the center yoke 11a, 11b crosses the coil6a, 6b, and the magnetic flux passing between the front side of themagnet 9a, 9b and the front side of the magnet 8a, 8b crosses the coil7a, 7b. When a current is caused to flow in the AF coil 6a, 6b, theforces exerted on both the coils are in the same direction (if an upwardforce is exerted on the coil 6a, an upward force is also exerted on thecoil 6b). When a current is caused to flow in the TR coil 7a, 7b, theforces exerted on both the coils are in the opposite directions (in FIG.4, if a rightward force is exerted on the coil 7a, a leftward force isexerted on the coil 7b).

As illustrated in FIG. 4, since the AF coils (6a, 6b) and TR coils (7a,7b) as drive means, all magnetic circuits 8 through 11, the supportsprings 12a through 12d as support means and the fixing means are allprovided on the support pin side of the object lens tip in the direction(along the line III--III in FIG. 4) in which the object lens 3 and thesupport pin 5 are connected (, or since those elements are disposed onlyon the left side of the object lens 3 as illustrated in FIGS. 3 and 4),the bias magnetic field generator will be described below can be easilyprovided with almost no spatial problem being caused by thetwo-dimensional actuator of the object lens drive means (, or withoutbeing obstructed by the actuator). Consequently, the distance betweenthe bias magnet and the beam spot focused point F (the focal point ofthe object lens 3 on the recording film 1) can be reduced, and theintensity of the bias magnetic field at the beam spot focused point canbe assured even if the bias magnet size is small.

Since the bias magnetic field generator of the permanent magnet ismounted on the movable head so that it is disposed on the object lensside of the recording medium and equal to or lower than the height ofthe object lens or the object lens drive, it is possible to sufficientlyreduce the distance between the permanent magnet and the beam spotfocused point on the recording medium. Also, the vertical magnetic fieldof an intensity necessary for the erasing and recording operations canbe generated and applied at the beam spot focused point by the smallbias magnetic field generator. In addition, the magnetooptical-diskrecording and/or reproducing apparatus can be small-sized and reduced inits height.

Since the bias magnetic field generator including the permanent magnetcannot be disposed under the beam spot, the bias magnetic fieldgenerator in this embodiment is provided on the opposite side of theobject lens to the object lens drive and support means and along therecording medium surface, thereby making it possible to reduce theheight of the apparatus. If the magnetic pole of the permanent magnet istilted from the direction perpendicular to the recording medium, themagnetic field component perpendicular to the recording medium can befurther strengthened at the beam spot focused point.

Since the permanent magnet and the means for rotating this magnet areplaced in a tightly closed container, and since the permanent magnetdrive coil is buried in this tightly closed container by molding or thelike as a part of the container, the bias magnetic field generator canbe further small-sized and reduced in its height.

Moreover, since the permanent magnet itself is formed as a rotor, anddriven to rotate by the force due to the interaction between themagnetic field from the permanent magnet and the current flowing in thepermanent magnet drive coil, a special mechanism for the rotation of thepermanent magnet is not necessary.

The bias magnetic field generator including the permanent magnet isprovided on the opposite side of the object lens to the object lensdrive and support means on the movable head as described above. Thepermanent magnet is magnetized in the rotation diameter direction andits rotation axis is parallel to the surface of the recording medium andlies in the radius direction of the recording medium. The magnetic fieldfrom the permanent magnet is symmetrical with respect to the center ofthe magnetization, and the magnetic lines of force emerge from theN-pole of the permanent magnet, pass through the beam spot focusedpoint, and turn 360 degrees, entering the S-pole. Since the permanentmagnet is located not just under the beam spot focused point butslightly deviated therefrom, the angle of the magnetic field at the beamspot focused point is substantially determined by the relative positionof the permanent magnet. Thus, by setting the rotation angle of thepermanent magnet a predetermined value, it is possible that theintensity of the magnetic field perpendicular to the recording medium atthe beam spot focused point is brought to a certain range (desirably tothe maximum value). The permanent magnet is set to a rotational position(reference angle) at which the vertical field component at the beam spotfocused point from one pole is the maximum, and to the other rotationalposition which is 180 degrees larger than this reference angle and atwhich the vertical field component at the beam spot focused point fromthe other (opposite) pole is the maximum. One of these angular positionsis for the erasing mode, and the other one is for the recording mode.Since the permanent magnet is set at these positions, the distancebetween the beam spot focused point and the permanent magnet can bereduced so that a large magnetic field can be applied at the beam spotfocused point.

In order to set the permanent magnet at the two different angularpositions, it is necessary to use rotation drive means and angle settingmeans. According to this invention, the permanent magnet itself is usedas a rotor for the rotation means, and the drive coil as a fixed part issimply placed in the magnetic field which is generated therefrom. Thisdrive coil is formed of a pair of saddle-type coils which are oppositeto the N-pole and S-pole of the permanent magnet and have portionsparallel to the rotation axis of the permanent magnet. A rotating effectis generated by the interaction between the current flowing in the coilsand the magnetic field from the permanent magnet.

The angle setting means can be realized by use of a mechanical stopperor by a pulse motor which is used as the rotation means and toelectromagnetically set the angles. According to this invention,considering the accuracy of operation and the reduction of the timenecessary for the magnet to be completely stopped after rotation, thedetection means is provided for rotation angles, and the output from thedetection means is fed back to the drive coil in order to rotate thepermanent magnet of the small-size, small rotation radius and lowrotation moment. Thus, the permanent magnet as a rotor can be controlledto turn 180 degrees at a high speed and to be stably and accurately heldat the two angular positions.

The construction of the bias magnetic field generator will be describedwith reference to FIGS. 6 and 7. FIG. 6 is a perspective view of thebias magnet drive saddle-type coils. FIG. 7 is a cross-sectional view ofthe bias magnetic field generator. A bias magnet 13 magnetized in onedirection perpendicular to the center axis is rotatably supported by ashaft 20 which is inserted in an aperture provided at the center, and byball bearings 18a, 18b engaged with the opposite ends of the shaft 20.

The ball bearings 18a, 18b are inserted and supported in a coil cover 14which is molded in a cylindrical shape with one end closed. The coilcover 14 has saddle coils 15a, 15b integrally buried and fixed thereinby molding. The opening side of the coil cover 14 is closed by a lid 19,and the coil cover 14 and the lid 19 are engaged and bonded to be fixed.Two Hall elements 17a, 17b are mounted on a sensor support plate 16. Thesensor of the two Hall elements is fixed at the coil-butt region of thecoil cover 14. The coil cover 14 is supported by a bias magnet holder 26in such a manner that the line, L along the coil-butt region at whichthe two saddle-type coils are combined is tilted an angle A from theline perpendicular to the magnetooptical-disk as shown in FIG. 3.

The Hall elements 17a, 17b produce outputs in accordance with thedensity of the magnetic flux which penetrates each Hall element. Theoutput difference between the two Hall elements 17a, 17b is fed back tothe saddle-type coil 15 by the control system shown in FIG. 8. Thesaddle-type coil 15 is formed of two saddle-coils 15a, 15b in series. Adifferential amplifier 27 shown in FIG. 8 produces the output differencebetween the Hall elements 17a, 17b.

The differential output is supplied through a phase-lead compensationcircuit 28 to a switching circuit 29. The switching circuit 29 respondsto a command from a separately provided controller to select one of aterminal for a constant output Vc and the other terminal which isconnected to the phase-lead compensation circuit 28. The output from theswitching circuit 29 is amplified by a drive circuit 30, and the outputcurrent from the amplifier is caused to flow in the saddle-type coil 15.

The basic operation of the bias magnetic field generator will bedescribed below. The basic operation includes three operations: thedetection of the polarity of the bias magnetic field, the detection ofthe fact that the bias magnet has entered a normal range of angles, andthe inversion to a necessary polarity. First, with reference to FIG. 9,a description will be made of the Hall elements 17a, 17b, the sum signaland difference signal therefrom and the strength H of the magnetic fieldperpendicular to the recording film 1 at the beam spot focused point Fwhen the bias magnet 13 is rotated once from the reference angle A (theline L) shown in FIG. 3. It is assumed that the magnetic field H isequal to or higher than a value necessary for the erasing mode when thebias magnet 13 is in the angular range of 0 degree through a₁ degree anda₄ degree through 360 degrees and that the magnetic field H is equal toor lower (the absolute value becomes large) than a value necessary forthe recording mode when the bias magnet is in the angular range of a₂degree through a₃ degree. In addition, it is assumed that the sum outputat each angle of a₁ through a₄ degrees is S₁ through S₄ and that thedifferential output at each angle is D₁ through D₄. Since the magneticfield strength (the component perpendicular to the recording film 1) Hat the beam spot focused point F of the recording film 1 and the outputsfrom the Hall elements 17a, 17b change like a sine wave as shown in FIG.9, the range of bias magnetic field H suitable for the erasing mode canbe confirmed from the fact that the sum output is a larger value of S₁,S₄ or above, and surely detected from the fact that the differentialoutput D is a value between D₄ and D₁.

Similarly, the range of bias magnetic field H suitable for the recordingmode can be confirmed from the fact that the sum output is a smallervalue of S₂, S₃ (a larger absolute value) or below, and surely detectedby the fact that the differential output D is a value between D₂ and D₃.

The polarity of the bias magnetic field can be determined by the valueof the sum output since the sum output S changes in the same way as thebias magnetic field H as shown in FIG. 9. In other words, when the sumoutput is S₁ or S₄ or above, it is on the erase side, and when the sumoutput is S₃ or S₁ or below, it is on the recording side. It is easilyunderstood that the polarity itself can be determined even by thenearest value to the central value of the sum output (, or from the factthat the absolute value of the sum output is the smallest).

When the differential output D is in a range from D₄ to D₁ or from D₂ toD₃, the bias magnet is decided to be in a correct range of angle. If thepolarity is not necessary to decide, it must be detected for the correctangle range that the differential output S lies between the large valueof D₃, D₄ and the small value of D₁, D₂. When the differential output Dis zero, the absolute value of the sum output S is the maximum.

The inversion of the bias polarity will be mentioned with reference toFIG. 10. The magnetic field applied to the saddle-type coil 15 changeslike a sine wave in accordance with the rotation angle of the biasmagnet 13. Thus, if a constant drive current i is caused to flow in thesaddle-type coil 15, the drive torque, Tr of the bias magnet 13 changeslike the magnetic field applied to the saddle-type coil. If the biasmagnet 13 starts rotating from the position in which the magnetizationdirection coincides with the coil-butt region of the saddle-type coil,the drive torque exerted on the bias magnet changes to the deceleratingdirection when it lies at a rotation angle of 90 degrees or above, andthe rotation speed becomes zero when it rotates through 180 degrees. Ifthe same drive current is further caused to flow, the magnet returns tothe initial angle. The time, T in which the rotation speed becomessubstantially zero from the start of the rotation is predetermined.Then, the switching circuit 29 is changed to the constant input Vc sideby the control system shown in FIG. 8, and the bias magnet is rotateduntil the lapse of the time T. Thereafter, the switching circuit 29 ischanged to the phase compensation circuit 28 side position, bringingabout the angular position determining control system. Thus, thefeedback control system is operated so that the differential output ofthe Hall elements 17a, 17b is zero, and as a result that the magnet 13is stably kept at a predetermined angular position. In this way, it ispossible to make the inversion and holding of the bias magnetic field.In order to make the bias magnet 13 at a constant initial angularposition, it is necessary that when the power supply is turned on theswitching circuit 29 shown in FIG. 8 be controlled to change to thephase compensation circuit side position so that the magnetizationdirection of the bias magnet 13 coincides with the coil-butt region ofthe saddle-type coil 15.

It can be considered that the magnetic field generated by the currentflowing in the saddle-coil 15 is small and has almost no effect on thebias magnetic field or others. If this field is considerably large, thebias magnetic field generator must be designed considering this effect.

In the above embodiment, although the sum output S of the Hall elements17a, 17b, when the bias magnet 13 lies at a rotation angle 8, changeslike a sine wave same as the vertical field strength H at the beam spotfocused point on the recording film 1, it does not always change like asine wave of the same phase depending on the relation between theangular position of the Hall elements relative to the bias magnet 13 andthe angular position of the beam spot focused point. Thus, in this case,in order to obtain a sine wave of the same phase, it is necessary toadjust the angular position of the mounted Hall elements 17a, 17b or theoutput phase of the Hall elements 17a, 17b.

In addition, the two-dimensional actuator has provided therein amechanism for preventing excess friction force from generating in thepin support mechanism by cancelling out the effect of the gravity by theforce of a magnet when the apparatus is placed with its top up. Thismechanism is designed to be able to rotate under the action from theoutside of the apparatus, and to affect the two-dimensional actuatoronly when the apparatus is placed with its top up. Thus, themagnetooptical-disk recording and/or recording apparatus according tothis embodiment can be stably operated not only when it is placed on itstop up but also when it is placed with its side down.

FIGS. 11A and 11B show examples of the use of the magnetooptical-diskrecording and/or reproducing apparatus of the invention in aninformation processing system such as a drawing retrieval system. FIG.11A shows an example of the use in which the magnetooptical-diskrecording and/or reproducing apparatus 116 is placed with its side down,and FIG. 11B shows the other example of the use in which themagnetooptical-disk recording and/or reproducing apparatus 116 is placedwith its top up. In this drawing retrieval system, the drawingsregistered in the magnetooptical-disk medium can be retrieved by a keyboard 117, and the selected diagram can be indicated on a display 118 sothat the user can examine the details of the drawing. If a scanner orprinter, though not shown, is connected to this system, it is possibleto construct a drawing management system in which the drawings can beregistered, retrieved and printed.

The environment in which the magnetooptical-disk recording and/orreproducing apparatus of the invention is used as in the drawingretrieval system shown in FIGS. 11A and 11B is like the general officewhich does not so consider the effect of dust. Therefore, theimprovement in the dust prevention is one of the main subjects for thedevelopment of the magnetooptical-disk recording and/or reproducingapparatus.

With reference to FIG. 12, a description will be made of the dustresistance improvement in the magnetooptical-disk recording and/orreproducing apparatus of the invention. In order to increase the dustresistance of the magnetooptical-disk recording and/or reproducingapparatus, it is most effective to place the disk and the movableportion of the optical head in a single, tightly closed box as is clearfrom the results of many experiments for dust resistance which wereconducted by the present inventors. The magnetooptical-disk recordingand/or reproducing apparatus of the invention has a feature in the diskexchangeability, and needs that the disk (cartridge) be inserted in andejected from the apparatus. Thus, it is difficult to make the apparatuscompletely tight like the magnetic disk recording and/or reproducingapparatus, but it is possible to make it quasi-tight.

FIG. 12 is a perspective view of one example of the magnetooptical-diskrecording and/or reproducing apparatus of the invention. In FIG. 12, theportions which are not concerned with the dust resistance improvementare omitted. As described with reference to FIGS. 2A and 2B, the frontpanel 101 is provided on the front of the apparatus, and the slot 102for the cartridge which is provided in the front panel 101 has a doubleflap provided. This double flap almost suppresses dust from entering theapparatus through the slot 102. The top and sides of the apparatus aresurrounded by a metal plate cover 123 so that dust can be absolutelyshut off. A partition wall 124 is provided at the back of the apparatusto lie between the fixed portion 106 and movable portion 107 of theoptical head shown in FIG. 2. The partition wall 124 has an aperture ofabout 6 mm in diameter bored through which the laser beam is passed, butthis aperture is blocked by a glass plate 125 which the laser beam canpenetrate so that dust can be prevented from entering the apparatus fromthe back. Also, the circuit board 104 is provided on the underside ofthe apparatus so as to block dust not to enter the apparatus. However,even under these countermeasures the metal plate cover 123 and thecircuit board 104 are produced with a poor accuracy, or have gapsthrough which dust may probably enter. Therefore, a packing 126 forpreventing dust not to enter are provided on the places where the gapsare easy to occur, such as the junctions between the metal plate cover123 and the partition wall 124 and between the partition wall 124 andthe circuit board 104. Since the surrounding of the housing in which thedisk cartridge and the movable portion of the optical head are placed isalmost completely tightly closed, the dust resistance can be increasedten times or above as compared with the conventional apparatus.

FIG. 13 is a basic circuit block diagram useful for explaining therecording and reproducing operations of the magnetooptical-diskrecording and/or reproducing apparatus of the invention. Amagnetooptical-disk 300 of which the recording film is made of aTbFeCo-based perpendicular magnetic film is rotated at 3000 rpm by aspindle 320 and information is recorded, reproduced and erased from therotating disk by the optical head.

The optical head for recording and reproducing can be divided into thefixed portion 106 and the movable portion 107. The fixed portion 106 hasmounted thereon a high-power semiconductor laser 301 which generates alaser beam of 30 mV, maximum and of a wavelength of 780 nm. The laserbeam emitted from the semiconductor laser 301 is converted into aparallel beam by a collimator lens 302, and further converted into aparallel beam of substantially a circular shape by a beam shaping prism303. This parallel beam is incident to a first beam splitter 304. A partof the incident beam to the first beam splitter 304 is reflectedtherefrom into a first optical detector 305, and the remaining part ispassed through the beam splitter and conducted through a dust preventingglass plate 118 to the movable portion 107 of the optical head. Themovable portion 107 has a mirror 306 fixed. The laser beam reflectedfrom the mirror 306 toward the disk 300 is focused by a focus lens 307which is supported on the two-dimensional actuator, and passed throughthe base of the disk 300 to form a beam spot on the recording film.

The laser beam reflected from the recording film of the disk 300 ispassed through the focus lens 307, mirror 306 and glass plate 118 andincident to the first beam splitter 304 of the fixed portion 106. A partof the incident beam is reflected therefrom. The laser beam reflectedfrom the first beam splitter 304 is incident to a second splitter 308. Apart of the incident beam is reflected therefrom and converted into afocused beam by a first convex lens 309. Then, the focused beam isseparated into two perpendicular polarized beams by a macro PBS(polarized beam splitter) 310, and the two polarized beams are incidentto an optical detector 311 having two independent photosensitiveportions. The laser beam passed through the second beam splitter isconverted into a focused beam by a diffracting lattice 312 and a secondconvex lens 313. The focused beam is passed through a cylindrical lens314 and incident to a third optical detector 315 which has eightindependent photosensitive portions.

The output from the first optical detector 305 is supplied to a laserpower control circuit 200. The laser power control circuit 200 generatesa laser power control signal on the basis of the output from the firstoptical detector 305. This laser power control signal is supplied to thelaser drive circuit 210, controlling the laser power upon reproductionto be constant. In this embodiment, the output from the focusing lens307 is controlled to have a power of 1.5 mW.

The second optical detector 311 has two independent photosensitiveportions, and thus produces two separate outputs, which are supplied toa head amplifier 201. The third optical detector 315 has eightindependent photosensitive portions, and thus produces eight separateoutputs, which are supplied to the head amplifier 201.

FIG. 14 shows the shapes of the respective photosensitive portions ofthe second optical detector 311 and third optical detector 315, and thebasic construction of the head amplifier 201. A sum signal 202 of twooutputs from the second optical detector 311 is used to reproduce thepreformat signal which is formed at the very small pits on the base ofthe disk 300. The preformat signal is a header signal includinginformation of the track address and sector address. A differentialsignal 203 of the two outputs is used to reproduce a magnetoopticalsignal recorded on the perpendicularly magnetized film. A signal 204, ofthe addition and subtraction of the outputs of the inner fourphotosensitive portions shown in FIG. 14, of the eight photosensitiveportions of the third optical detector 315, is used as a focus servosignal. A signal 205 of the addition and subtraction of the outputs ofthe outer four photosensitive portions is used as a tracking servosignal. A signal 206 of all addition of the outputs of the outer fourphotosensitive portions is used to detect a track cross signal togetherwith the signal 205.

The signals 204 and 205 are supplied to a servo/access control circuit207 and drives the two-dimensional actuator 11 which is mounted on themovable portion 7 of the optical head, so that the focus servo andtracking servo can be performed stably. The signal 206 is also suppliedto the servo/access control circuit 207 and used for access controltogether with the signal 205.

As to the reproduction of the information from the disk 300, the signal202 or 203 of the addition or subtraction of the outputs from the secondoptical detector 315 is supplied to a reproduced signal processingcircuit 208 where the data are discriminated. The output from thereproduced signal processing circuit is fed together with thereproduction clock to a logic circuit 209 where a logic process such asdemodulation of (1-7) RLL code and error correction by an ECC code isperformed. The data from the logic circuit is supplied through the SCSIinterface to the high-level apparatus.

As to the recording of information on the disk 300, if the informationbeing recorded on the disk from the high-level apparatus is received bythe logic circuit 209 through the SCSI interface, the logic circuit 209makes (1-7) RLL modulation and addition of an ECC code and so on,thereby converting it into a signal to be recorded on the disk. Thissignal is supplied to a laser drive circuit 210. The laser drive circuit210 responds to the signal from the logic circuit 209 to cause a certaincurrent to flow in the semiconductor laser 301, thereby intensivelyexciting the laser so that information can be recorded on the disk. Atthis time, the magnet for recording and erasing is controlled togenerate a magnetic field for recording by a rotation control circuit211 for the magnet in response to the command from the logic circuit209.

In order that the information recorded on the disk is erased, the laserdrive circuit 210 causes a direct current to flow in the semiconductorlaser 300 under the control of the logic circuit 209, therebyextensively exciting the laser 300. At this time, the rotation controlcircuit 211 responds to a command from the logic circuit 209 to causethe magnet for recording and erasing to generate a magnetic field forerasing.

The recording, reproducing and erasing operations have been brieflydescribed above. The technique for the recording, reproducing anderasing operations according to this invention will be mentioned indetail with reference to drawings.

In the ZCAV recording system, the user's region on the disk is dividedinto a plurality of zones in the radius direction, and the number ofsectors per track is changed for each zone.

FIGS. 15 and 16 show one example of the division of the user's regioninto zones. In FIG. 15, the user capacity per sector is 1024 bytes, theformat capacity (total capacity) is 1409 bytes, and the number of tracksper zone in 748. In FIG. 16, the user capacity per sector is 512 bytes,the format capacity (total capacity) is 801 bytes, and the number oftracks per zone is 403. For both cases, before recording of information,it is modulated by the (1-7) RLL code. The disk is rotated at a rate of3000 rpm. For both cases, the track pitch is 1.34 μm, and the user'sregion is in a range from 60 mm to 120 mm in diameter. From FIGS. 15 and16, it will be understood that in this embodiment the difference betweenthe numbers of sectors in adjacent zones is 1, and that the frequency ofthe necessary clock for recording and reproduction is proportional tothe number of sectors per track.

FIG. 17 is a basic circuit block diagram of the synthesizer. Referringto FIG. 17, there are shown frequency dividing circuits 212, 213, aphase detector 214, a charge pump 215, and a voltage controlledoscillator 216 (VCO). The frequency dividing ratios of the frequencydividing circuits 212, 213 are determined by integers N and M which areset in registers 217, 218, respectively. Usually, the output signal froma crystal oscillator is supplied to the synthesizer. If the oscillationfrequency of the oscillator is represented by Fin, the frequency of theoutput from the synthesizer is the Fin multiplied by M/N.

Therefore, if M is selected to be equal to the number of sectors pertrack or an integer multiple of the sector number, and if Fin and N arearbitrarily selected, the clocks for all zones in the ZCAV recordingsystem can be theoretically obtained by simply changing the value of M.For example, for the case of zone division shown in FIG. 15, theoscillation frequency Fin of the crystal oscillator, N and M are set to11.413 MHz, 27 and twice the number of sectors per track, respectively.For the case of zone division shown in FIG. 16, the oscillationfrequency Fin of the crystal oscillator, N and M are set to 12.976 MHz,27 and the number of sectors per track, respectively.

Thus, if two crystal oscillators are provided and switched, both casescan be supported in which the user capacity per sector in FIG. 15 is1024 bytes and that in FIG. 16 is 512 bytes.

When the disk standardized by the ISO/IEC 10089 specification is rotatedat a rate of 300 rpm, the frequency of the clock necessary for therecording and reproduction is 18.495 MHz. If the crystal oscillator of11.413 MHz is used and if N and M are set to 93, a clock frequency ofabout twice that, or 36.994 MHz can be obtained. Thus, the frequency ofthis signal is divided by 2 by use of a known frequency dividingcircuit. Consequently, it will be understood that a new crystaloscillator is not necessary for recording and reproducing the disk whichis standardized by the ISO/IEC 10089. In the example shown in FIG. 15,the format capacity per sector is selected not to need a new crystaloscillator.

FIG. 18 is a basic circuit block diagram of the reproduced signalprocessing circuit 208 shown in FIG. 13. The output 202 or 203 from thehead amplifier 201 is supplied to the reproduced signal processingcircuit 208. First, a waveform equalizing circuit 220 corrects thelinear distortion of the waveform what is called the intercodeinterference. An automatic gain control (AGC) circuit 221 adjusts theamplitude of the reproduced signal of the densest pattern to beconstant. Then, edge detecting circuits 222 and 223 detect the frontedge and rear edge, respectively. The outputs from the edge detectingcircuits 222 and 223 are respectively supplied to their PLLs whichproduce reproduction clocks in synchronism with the front edge and therear edge. Since the two PLLs are simultaneously operated, this systemis called the double PLL. Data discrimination circuits 226 and 227discriminate the presence or absence, or 1, 0 of the edge signals by thereproduction clocks which are generated from the PLL circuits 224 and225. The outputs from the data discrimination circuits 226 and 227 aresupplied together with the reproduction clocks to a reproductionsynthesizing circuit 228 of the logic circuit 209 shown in FIG. 13,where a normal binary signal of 1, 0 is produced. The timing in whichthe two signals are compounded is detected from the VFO portion(determined by the timing of the front edge and rear edge) at the headof the recorded data. The output from the reproduction synthesizingcircuit 228 which is a normal binary signal of 1, 0, is demodulated intothe original data by a (1-7) RLL demodulation circuit 229. The data isprocessed to undergo error correction by an ECC code, and then the userdata is extracted from the data.

In the case of the mark position recording, although the output from thehead amplifier is necessary to be first differentiated by adifferentiation circuit and processed for AGC or the like, thisinvention does not use any differentiation circuit as will be obviousfrom the above description. Here, this system is called the originalwaveform reproduction system.

The fundamental operation of the waveform equalizing circuit 220 and theeffect thereof will be described in detail with reference to FIGS. 19and 20. FIG. 19 is a basic circuit block diagram of an example of thewaveform equalizing circuit 220, or a three-tap transversal filter. Theoutput 202 or 203 from the head amplifier 201 is supplied to variabledelay elements 3301 and 3302, in serial order so that three differentsignals S1(t), S2(t+D), S3(t+2D) where t is time can be produced as aresult of delaying it by D (ns) in each element. The signals S1(t),S2(t+D), S3(t+2D) are amplified by a factors of K1, K2 and K3,respectively, and then fed to an adder 3306 which produces anequalization output EQ(t). According to an experiment, when delay D isequal to the period (80 ns for the innermost periphery, 40 ns for theoutermost periphery) of the reproduction clock and when K2, K1 and K3are selected to be 1, 0.06 and 0.06, respectively, the best result canbe obtained. FIG. 20 shows the result of the experiment.

This invention employs the 1-7 modulation system. The prior art employsthe 2-7 modulation system for the magnetooptical-disk. FIG. 21 shows therule of the 1-7 modulation system, and FIG. 22 shows the comparisonbetween the characteristics of the 1-7 modulation system and 2-7modulation system. From FIG. 22 it will be seen that the 1-7 modulationsystem is more advantageous for high density recording.

The trial writing control system in this invention will be mentionedbelow.

The trial writing control is intended to remove the factors ofdeterioration of the recorded state such as the environmentaltemperature change, sensitivity dispersion of recording disks andcharacteristics dispersion of recording apparatus. This trial writingcontrol system is one of the very effective systems for achieving alarge storage capacity of 1 GB/side or above.

The trial writing control is fundamentally to alternately record therepetitive closest pattern and coarsest pattern and detect thedifference ΔV between the central levels of the reproduced signal. Asshown in FIG. 23C, the difference ΔV changes with the change ofrecording power, P1 through P8. In this embodiment, the recording powerP4 for ΔV=0 is the optimum recording power. In practice, the disk has atrial-writing region in each zone of ZCAV (specifically in one or twotracks). The special pattern mentioned above is recorded in a pluralityof sectors of the trial writing region with the recording power beingslightly changed for each sector. Then, the plurality of recordedsectors are reproduced. The reproduced signal central level of theclosest pattern is detected from the reproduced signal including theclosest pattern and the coarsest pattern (FIG. 23A) by a sample pulse(SAMPLE 1-P) of FIG. 23B for the closest pattern. The reproduced signalcentral level of the coarsest pattern is detected therefrom by a samplepulse (SAMPLE 2-P) for the coarsest pattern. The ΔV of each sector isobtained from the difference between both the central levels. Therecording power for ΔV=0 is calculated and the calculated value ofrecording power is stored in a memory within the apparatus and useduntil the next trial writing is performed. Since the recording power isgenerally changed for each zone, the value of the recording power iscalculated in each of the three zones of the inner, medium and outerperipheries upon insertion of disk, and the values of the recordingpower in the other zones are determined by linear approximation from thevalues which were calculated in the three zones. After the insertion ofthe disk, the trial writing is made in proper zones at every constanttime, for example, every five minutes, and the values stored in thememory are corrected. The erasing power is also changed in associationwith the recording power which was obtained in the trial writing. Thistrial writing control is also performed as one of the error recoverieswhen a recording error or erasing error occurs, thereby increasing thereliability of the recording and erasing operations.

When the interfaces SCSI-1 and SCSI-2 to the high-level apparatus aresimultaneously supported, a problem is caused with the switching of SCSIcommands. The process for the simultaneous supporting is usuallycomplicated by the facts that the commands for supporting the SCSI-1 andSCSI-2 are different, that the interfaces are supported by the samecommand but differently processed, and that the SCSI bus is disconnectedor connected depending on the contents of the processing. In order toavoid these facts, this invention makes a table of the support commands.FIG. 24 shows one example of the table. In this table, flags of 8 bitsare provided for the commands of 00 through FF. The most significant bitof each flag indicates to support/not to support, and the second bitindicates to disconnect/not to disconnect the SCSI bus. The remainingsix bits indicate the contents of the command. The SCSI-1 or SCSI-2 canbe selected not only by normally switching the set positions of thejumper pins which are mounted in the apparatus, but also by the commandof SCSI (change definition).

We claim:
 1. A magnetooptical-disk recording and/or reproducingapparatus comprising:a 5.25 inch magnetooptical-disk having a storagecapacity of at least 1 GB/side with a ZCAV (Zoned Constant AngularVelocity) format in which a recording area is divided in a plurality ofzones in a radius direction so that a recording density of each zone issubstantially constant independent of said radius direction; and meansfor producing a recording mark with edges having information, therecording mark producing means including: a double Phase Locked Loop forindependently discriminating data independently applied to a front edgeand a tail edge, a trail writing control means for controlling settingof a recording power in accordance with previously writing data in atleast one regions of said magnetooptical-disk, a 1-7 modulation meansfor converting information to be recorded into a Run Length Limitingcode, and a direct edge detection means in which a gain of a reproducedsignal from said magnetooptical-disk is automatically adjusted byequalizing said reproduced signal without differentiating.
 2. Amagnetooptical-disk recording and/or reproducing apparatus according toclaim 1, wherein a magnet or electromagnetic coil for generating amagnetic field for recording and/or erasing is disposed on the same sideas an optical head for generating a beam spot for recording andreproduction, relative to said disk.
 3. A magnetooptical-disk recordingand/or reproducing apparatus according to claim 1, wherein a pluralityof tapped holes by which said magnetooptical-disk recording and/orreproducing apparatus is fixed within a housing are provided on lateralsides and bottom sides of said apparatus at the same positions as amagnetic disk recording and/or reproducing apparatus of equal size asthat of said magnetooptical-disk recording and/or reproducing apparatusand having a SCSI-2 interface to a high-level apparatus and supporting aSCSI-1 interface.
 4. A magnetooptical-disk recording and/or reproducingapparatus according to claim 1, wherein a cartridge including said diskwhich is loaded within said magnetooptical-disk recording and/orreproducing apparatus, and the movable portion of an optical head arehoused in a tightly closed structure, and a circuit board having asubstantial part of a circuit system for making a recording andreproducing process is mounted on an underside (on the opposite side ofthe optical head to said disk) of said tightly closed structure of saidapparatus.
 5. A magnetooptical-disk recording and/or reproducingapparatus according to claim 1, wherein a magnetooptical-diskstandardized by ISO/IEC 10089 specification can be recorded and/orreproduced without providing another crystal oscillator.
 6. A halfheight magnetooptical-disk recording and/or reproducing apparatuscomprising:a magnetooptical-disk having a storage capacity of at least 1GB/side with a Zoned Constant Angular Velocity formatting in which arecording area is divided in a plurality of zones in a radial directionwith a substantially constant recording density; a movable headincluding an object lens which forms a small optical spot on a recordingfilm of said magnetooptical-disk, said object lens facing a recordingmedium of said magnetooptical-disk; a bias magnetic field applying meansfor rotating a permanent magnet and inverting polarities of a biasmagnetic field perpendicular to said recording film, said bias magneticfield applying means being mounted in said movable head, said biasmagnetic field applying means having a height which is less than aheight of a driving apparatus for said object lens and being on a commonside of said magnetooptical-disk with said object lens; and means forproducing a recording mark including Phase Locked Loop means forindependently discriminating data applied to a front edge and a tailedge, a trial writing control means for controlling a recording powersetting in accordance with previously writing data in one or moreregions of said magnetooptical-disk, a modulation means for convertinginformation to be recorded into a Run Length Limiting code, and a directedge detection means for automatically adjusting a gain of a reproducedsignal from said magnetooptical-disk.
 7. A magnetooptical-disk recordingand/or reproducing apparatus according to claim 6, wherein said biasmagnetic field applying means is disposed in parallel with a surface ofsaid magnetooptical-disk and on a side opposite of said object lens tosaid driving apparatus of said object lens and support means.
 8. Amagnetooptical-disk recording and/or reproducing apparatus according toclaim 7, wherein said permanent magnet and said bias magnetic fieldapplying means for rotating said permanent magnet are housed in atightly closed container.
 9. A magnetooptical-disk recording and/orreproducing apparatus according to claim 8, wherein a drive coil fordriving said permanent magnet is integrally buried in said tightlyclosed container for housing said bias magnetic field applying means asa part of said tightly closed container.
 10. A magnetooptical-diskrecording and/or reproducing apparatus according to claim 6, whereinsaid permanent magnet of said bias magnetic field applying means isformed as a rotor to be rotatable by an interaction of a magnetic fieldfrom said permanent magnet and a drive current flowing in the drive coilof said permanent magnet.
 11. A magnetooptical-disk recording and/orreproducing apparatus according to claim 10, wherein said permanentmagnet of said bias magnetic field applying means is magnetized in arotation diameter direction and the drive coil of said permanent magnethas a portion which faces an N-pole and S-pole of said permanent magnetand is parallel to a rotation axis of said permanent magnet.
 12. Amagnetooptical-disk recording and/or reproducing apparatus comprising:amovable head having an object lens provided to face saidmagnetooptical-disk and form a very small beam spot on a recording filmof said disk; a bias magnetic field generator for rotating a permanentmagnet to invert a polarity of a bias magnetic field perpendicular tosaid recording film, said bias magnetic field generator being mounted onsaid movable head being disposed on said object lens side of saidmagnetooptical-disk and to be lower than a height of an object lensdrive actuator, said permanent magnet of said bias magnetic fieldgenerator being formed as a rotor to be rotatable by an interaction of amagnetic field from said permanent magnet and a drive current flowing ina drive coil of said permanent magnet, said permanent magnet of saidbias magnetic field generator being magnetized in a rotation diameterdirection and the drive coil of said permanent magnet having a portionfacing an N-pole and S-pole of said permanent magnet and being parallelto a rotation axis of said permanent magnet, said permanent magnet ofsaid bias magnetic field generator being disposed on an opposite side ofsaid object lens from the object lens drive and support means of saidobject lens and the rotation axis of said permanent magnet beingparallel to a surface of said magnetooptical-disk and in a radiusdirection of said magnetooptical-disk.